GB804325A - Hydrostatic axial piston variable ratio drive - Google Patents

Abstract

804,325. Variable-speed gear. EBERT, H. March 9, 1956 [March 21, 1955], No. 7507/56. Class 80 (2). [Also in Group XXIX] A continuously variable ratio hydrostatic piston gear having a hydrostatic pump and a hydrostatic motor, the compression and suction chambers of which are connected with each other, is characterized by both the pump and motor having tiltable cylinder blocks, and having associated with them a differential gear comprising a driving sun-wheel associated with one of the hydrostatic piston assemblies, and a reaction element associated with the other hydrostatic piston assembly, this reaction element being either a planet wheel carrier or a component having internal teeth meshing with the planet gears. In one form, Fig. 1, a driving shaft 2 carries a bevel sun-gear 4 meshing bevel planet gears 7 rotatable in a carrier 9, itself rotating to drive through a gear train 10, 11, a hydrostatic piston assembly 13 the cylinder block of which can be tilted about a pivot point 15.to control the volume of liquid flowing therethrough per revolution. A second bevel sungear 5 is fast on a driven shaft 3 and drives through a gear train 22, 23 to a second hydrostatic piston assembly 20 similarly having a tiltable cylinder block. The suction and pressure side of the hydrostatic assemblies 13, 20 are permanently, connected together. In the position shown, rotation of the driving shaft 2 causes the output shaft to be driven backwards with a ratio of 1 : - 1, the hydrostatic unit 20 being so adjusted that although the driven shaft 3 rotates without causing it to pump any liquid, the hydrostatic unit 13, which is adjusted to pump the maximum quantity of fluid, is unable to pump any into the unit 20, the pistons of which cannot reciprocate, and the planet carrier 9 is thereby held stationary. By tilting the hydrostatic unit 13 about its pivot point 15 until its axis is parallel with the main axis of the gear, and tilting the hydrostatic unit 20 to its maximum inclination to the main axis of the gear, the driven shaft 3 of the gear is held stationary while the planet carrier 9 is allowed to rotate freely. Intermediate settings of the hydrostatic units 13, 20 allow intermediate ratios to be obtained. In a modification, interengaging planet gears 28, 28a, Fig. 2, are mounted in a planet carrier 29 connected through a quill shaft 42 and a gear train 43, 44 to a hydrostatic unit 30. This unit again has a main cylinder block tiltable about a pivot point, and is formed with a rotatable cylinder block 32, opposed to the cylinder block of the main, tiltable cylinder block, having pistons 34 therein. The pistons in the main cylinder block have holes therein connected by conduits in connecting rods 38, 36 to holes in the pistons 34 in the cylinder block 32. The arrangement is such that the hydrostatic pressures generated in the two interconnected units tend to balance each other out, instead of reacting upon the bearings supporting the unit. The driven shaft 3 of the gear is connected through a train 46, 47 to a similarly arranged hydrostatic unit 31. In a similar modification, Fig. 3 (not shown), the interengaging planet differential gear is arranged on the driven, instead of the driving, side of the gear. In yet another modification, the driving shaft 2 carries a sun-gear engaging a long planet gear 58, Fig. 4, in turn meshing a short planet gear 58a meshing a sun-gear on the driven shaft 3. The planet carrier is connected through a quill shaft 59 and a gear train 60 to two similar opposed hydrostatic units 54, 55 having tiltable cylinder blocks and connected to similar hydrostatic units 56,57 driven from the output shaft 3 of the gear. In the gears shown in Figs. 1-4, a 1: - 1 drive is obtained, with the driven shaft 3 turning in the opposite direction to the driving shaft 2. In a form in which the driving and driven shafts 2, 3 rotate in the same direction for a 1: 1 drive, a sun-gear 63, Fig. 5, on the driving shaft 2 engages planet gears 65 meshing internal teeth on a stationary part of the casing and carried by spindles in a carrier 66a also carrying planet gears 65a meshing a sun-gear 64 on the driven shaft 3. The planets 65a are in engagement with internal teeth in a ring member 66 connected through a quill shaft 67 and a gear 68 to a tiltable cylinder block hydrostatic piston pump 69 having a non-tiltable associated cylinder block 70. The driven shaft of the gear is connected through a gear 71 with two tiltable cylinder block hydrostatic piston motor assemblies 72, 73. In arrangements of the gear required to carry heavy loads, a single pump is arranged parallel with two motor units, the three units being equally spaced around the driven shaft, Figs. 6, 7 (not shown).